CPU HSF creating a humming noise through my speakers.

Finally after a loooong time I have my car-pc installed however the damn fan on the cpu heat sink is giving me really bad feedback though my speakers. Definitely is the fan because when I dis connect it the noise goes away but for obvious reasons I need to have it connected.

Any idea's ?

IF it's any help the psu is directly wired to my second battery and the switching power feed is from the cigarette lighter, my amps are also configured in the same manner.

Should I trigger the amps from the m4-atx power supply instead, will that single little pin actual be enough to turn on 3 amps ?